Agricultural planters are towed behind a tractor and generally consist of a hitch assembly, connected to the tractor, and a pair of wing booms, each wing boom coupled to the hitch assembly. The wing booms support a series of spaced row units that deposit seed, fertilizer or other granular material onto a planting surface, e.g., farm field. Because of the relatively large span of the wing booms, the planter frame typically includes a pair of draft links. Each draft link extends between the hitch assembly and one of the wing booms and is designed to add stability to the wing booms as the planter traverses the planting surface. In some planters, the wing booms are designed to fold forward against the hitch assembly. For such forward-folding planters, the wing booms will typically be folded forward when the planter is ready for transport. That is, a planter generally has a working position in which the wing booms are fully extended away from the hitch assembly and a transport position in which the wing booms are folded forward toward the hitch assembly. In the transport position, the width of the planter is greatly reduced which is advantageous for exiting the planting surface and for storage of the planter. Additionally, when being shipped, the planter will be placed in its transport position.
To expedite particulate matter deposition onto the planting surface, planter manufactures are adding length to the wing booms thereby allowing more row units to be mounted along the length of the wing booms. As a result, the length of the wing booms is becoming greater than the length of the hitch assembly. When the wing booms are retracted into the transport position, the outer ends of the wing booms may undesirably extend forward past the hitch of the towing vehicle, e.g., tractor. As such, large agricultural planters are typically equipped with a telescoping hitch assembly, rather than a fixed length, hitch assembly. More particularly, the hitch assembly includes a telescoping portion that increases the length of the hitch assembly as the wing booms are folded forward. The telescoping hitch assembly, therefore, provides clearance for the outer ends of the wing booms behind the tractor as the wing booms are retracted for transportation.
The draft links connected between the hitch assembly and the wing booms are typically hydraulic cylinders configured to extend and to retract, thereby causing the wing booms to move between the transport position and the working position. As the wing booms are folded forward, the draft links connected between the hitch assembly and the wing booms also cause the telescoping portion of the hitch assembly to extend to provide the aforementioned clearance for the wing booms. The required size of the hydraulic cylinder for the draft link is a function of several factors, such as the weight of the wing boom, the amount of extension required by the hitch assembly, and the location at which the draft link is connected to the wing boom. As the length of the wing booms is increased the weight of the wing boom increases, the amount of extension required by the hitch assembly increases, and the location at which the draft link is connected to the wing boom may change as well. Each of the factors contributes to an increase in the amount of force required to move the wing boom between the transport position and the working position and, therefore, to an increase in the size of the draft link.
Therefore, there is a need for an agricultural planter which provides an improved method for moving the wing boom between the transport position and the working position.
When the wing booms are extended, each boom acts as a lever arm with respect to the pivot point at which the boom is connected to the hitch assembly. If a wing wheel at the end of the boom encounters an obstacle, such as a rock, furrow, or the like, the force seen at the hitch assembly is multiplied by the length of the wing boom. With increasing lengths of the wing booms, the force that is required to be applied from the towing vehicle to the planter in order to overcome forces encountered at the ends of the wing booms is similarly increased. In addition, the additional length requires additional wing wheels to support the wing boom, and each wing wheel introduces additional forces to the hitch assembly such as additional rolling resistance or additional forces resulting from objects encountered in the field. The additional forces on the planter due to the increasing length of the wing boom require additional force applied to the planter from the towing vehicle and reduce maneuverability of the planter.
Therefore, there is also a need for an agricultural planter having improved maneuverability during operation.